Method of using rolling mill piercing points



Patented May 26, 1931 nrsur OFFICE HbMEB, F. TIELKE, OF CLEVELAND, OHIG METHOD OF USING ROLLING MILL PIERCING POINTS No Drawing.

This invention relates to the art of metal working, particularly metal piercing and tube making, and is especially concerned with a new and improved method of employing a plugs and piercing points in rolling mills.

' Heret-ofore the practice in using plugs and piercing points in rolling mills has been to employ the plug or point in a cold condition and remove it from the mill after the hot metal being worked had heated the plug or point up to a relatively high temperature, after which the part was removed and cooled. rapidly in water. Plugs and points so used have had comparatively short lives, i. e., they could be used only a small number of times before their usefulness was destroyed. The initial cost of parts,-such as plugs and points, is high and when they are of short life the resultant cost of the metal worked in mills, us-

Cl) ing such parts is high.

I have discovered that the length of life of articles such as plugs and piercing points can be materially extended and that this is particularly true where such articles are com- 23 posed of certain alloys which have been heat treated in a particular manner, preferred alloys and method of heat treatment being set forth and claimed in my co-pending application Serial No. 387,910, filed August 23, 1929.

:9 According to the present invention I employ as an alloy for rolling mill plugs and piercing points a high carbon steel composition, which preferably contains between about .7 5% and about 1.5% carbon, between about 16% and about 19% chromium, and

between about 2% and about 4% of cobalt.

Nickel may also.be present in the alloy in amounts between about 4% and about 2% and tungsten up to about 2% may be also used 'f desired. This composition is claimed in the foregoing identified co-pending application.

According to that application the foregoing alloys are first cast approximately to size and then ground to remove roughness or to bring the casting to the desired size if necessary, after which the casting is heat treated by being heated thoroughly at 2250 F, then cooled in air,-then reheated to about 1800 F.

m and quenched, and finally heated at a soaking Application filed. August 23, 1929. Serial No. 388,043.

temperature of about 1200F. for a considerable time, such as six hours.

The present invention is predicated on the. discovery that the life of plugs and piercing points of-the foregoing composition and heat treatment can be greatly extended if these parts are employed in a manner, which takes into account a proper heat control of the articles. For example, I prefer to use a piercing point substantially as follows: A point an of the foregoing composition and heat treatment is preheated to between about 900 F. and about 1200 F. before it is used in metal working. While so heated it is used in a rolling mill until after several passes of metal have been made thereover and the surface of the point becomes heated to a temperature well above 1200 F. The point is then removed and cooled slowly, i. e., in lime, mica or other slow cooling medium. When the point has been thus cooled to a temperature of between about 900 F. and about 1200 F.-it may be placed again in the rolling mill and used for working metal as before. In the event that the point cools in the slow cooling medium to below 900 F. it is preheated to between 900 F. and 1200 F. before being used again.

I have discovered that the use of such points and plugs in the described preheated 3o condition exerts a marked effect on the length of life of the point or plug and makes it possible to use these parts for many times the length of life of the plugs and points now in use. Instances have been known where a 5 point could be used according to my invention for more than sixty times the number of passes that the prior art points can normally be used.

I have found that the step of preheating the plugs and points of the foregoing composition and heat treatment to between 900 F. and 1200 F. before use removes any tendency the metal may have to crack as has been known with the similar metal not so preheated.

Moreover, the points or plugs of the foregoing composition and heat treatment exhibit the property of comparatively long life in contrast with similar articles of the prior art material even though not preheated as described herein, but only when cooled slowly in a slow cooling medium as above set forth, or in air. Quenching in water or the like will often result in shattering the material of the point or plugs after it has been heated highly in use.

By the word point as used in the claims is meant any type of piercing point or plug as well as any substitute or modifications of such elements such as a die.

Having thus described my invention so that others skilled in the art may be able to practice the same, what I desire to secure by Letters Patent is defined in what is claimed, it

' being understood that variations and chan es in the foregoing detailed description may e made without departing from the scope of my invention.

\Vhat is claimed is:

l. The method of operating a rolling mill including a point which comprises the steps of preheating the point to a temperature between about 900 F. and about 1200 F., inserting said point in the pass of the rolling mill and using the point while so heated to enter work passing through said pass until the surface thereof has been heated well above 1200 F.

2. The method of operating a rolling mill including a point which comprises the steps of preheating the point to a temperature between about 900 F. and about 1200 F., inserting said point in the pass of a rolling mill and using the point while so heated to enter work passing through said pass until the sruface thereof has een heated well above 1200 F., and then removing the high heated plu or point and cooling it in a slow cooling 3. The method of using a point in a rolling mill, which includes the ste s of preheating the point to a temperature etween 900 F. and about 1200 F., placing said point in the pass of a rolling mill and using the thus heated point for several passes until the surface thereof is heated well above 1200 F., and then cooling the point in a slow cooling medium, such as lime, to a temperature below about 1200 F.

' 4. The method of using a point in a rolling mill which comprises heating the point to a temperature of between 900 F. and about 1200 F.; placing said point in the pass of a rolling mill and using it in a rolling mill while so heated for several passes, then cool ing the point in a slow cooling medium, and reusing the plug or point in a rolling mill at an initial temperature of between 900 F. and about 1200 F.

In testimony whereof I hereunto aflix my signature this 20th day of August, 1929.

HOMER F. TIELKE. 

